annular bright field

**ABF** (Annular Bright Field) is a **STEM imaging mode that collects electrons at small-to-medium scattering angles** — providing contrast for both heavy and light elements simultaneously, solving HAADF's limitation of being insensitive to light atoms like oxygen, nitrogen, and lithium. **How Does ABF Work?** - **Detector**: Annular detector at low-to-medium angles (typically 11-22 mrad for a 22 mrad convergence angle). - **Contrast**: Atomic columns appear as dark spots on a bright background (absorptive contrast). - **Light Elements**: ABF can image O, N, Li, H columns that are invisible in HAADF. - **Combined**: Simultaneously acquire ABF and HAADF for complete heavy + light atom imaging. **Why It Matters** - **Light Atom Imaging**: The breakthrough that enabled direct imaging of oxygen columns in oxides, nitrogen in nitrides, and lithium in battery materials. - **Complete Structure**: HAADF shows cations. ABF shows anions. Together, the complete crystal structure is imaged. - **Battery Materials**: Essential for studying lithium-ion battery cathodes where Li positions are critical. **ABF** is **the light-atom detector** — the STEM mode that makes lightweight atoms visible, completing the picture that HAADF alone cannot provide.